As a result of increase of components per chip, the structure of memory or non-memory semiconductor devices has been complicated, and the importance of step coverage has been increased when depositing thin film in great variety on the substrate.
In a metal oxide thin film manufacturing process such as chemical vapor deposition (CVD) or atomic layer deposition (ALD), the metalorganic compounds demand specific properties, such as high volatile nature, high temperature difference between evaporation and decomposition, low toxicity, chemical stability, heat stability, easiness of chemical synthesis and thermolysis.
Further, the metalorganic compounds should not be voluntarily decomposed nor have side reaction with other materials during the evaporation and conveying processes thereof. Particularly, in order to obtain good multi-components thin films, ratio of metal components introduced can be easily controlled and decomposition behaviors of metal precursors at deposition temperature should be similar each other.
As thin films for manufacturing semiconductors, metal nitrides, metal oxides, metal silicates or metals, etc. are usually used. Examples of representative metal nitrides are titanium nitride (TiN), tantalum nitride (TaN) and zirconium nitride (ZrN). The thin film of metal nitrides is effected as a diffusion barrier between a silicon layer of doped semiconductor and a wiring layer connecting semiconductor layers such as aluminum or copper.
The thin film of metal nitrides is effected as an adhesion layer when tungsten thin films are deposited on the substrates.
Examples of representative metal silicates for manufacturing thin films are titanium silicates and tantalum silicates. The thin film of metal silicates is effected as an adhesion layer between silicon substrates and electrodes/wiring materials/diffusion barriers. When depositing metal thin film on silicon layers, a metal silicate such as titanium silicates or tantalum silicates is used to improve adhesion.
It is known that metal oxides such as alumina (Al2O3), titania (TiO2) or tantalia (Ta2O5) etc., are used for capacitors of semiconductor devices, and have dielectric constants (∈) higher than those of silicates (SiO2), and these materials are utilized in manufacturing memory semiconductors having large scale integration and/or high capacity.
As described above, the selection of precursor is the most important requirement in order for deposited thin films to have good properties. For example, when titanium nitrates (TiN) are deposited on substrates using titanium chlorides (TiCl4), this precursor has the following problems despite of good economic feasibility thereof.
Chlorine atoms presented in precursors are introduced into the deposited titanium nitride thin film, and induce corrosions of aluminum wiring materials. In addition, as deposition temperature is high (around 600° C.), this process cannot be adopted when wiring materials are aluminums having low melting point. Further, during deposition processes, non-volatile materials, such as titanium chloride ammonium complexes (TiCl4:NH3)x and ammonium chloride salts (NH4Cl) are formed and these materials are accumulated in thin films, the produced semiconductor chips induce critical demerits.
Additionally, tantalum chlorides (TaCl5) or zirconium chlorides (ZrCl4) are used in order to deposit tantalum nitrides (TaN) film or zirconium nitrides (ZrN) film on substrates. However, above chlorides are not easy to use as precursors, since these are solids, which cannot supply a sufficient vapor for deposit processes.
Further, either processes for forming titanium nitride (TiN) films using titanium amides[Ti(NR2)4:R═CH3 or C2H5] or processes for forming tantalia (Ta2O3) films using tantalum ethoxides are developed for dielectric films, these precursors are unstable and dangerous materials.
Zirconia (ZrO2) has higher dielectric constant (∈) than that of silicon dioxide (SiO2). And when it is applied in capacitors of semiconductor devices, high integrated and high capacity memory semiconductors can be obtained.
As zirconium compounds which are most frequently applied in metaloganic chemical vapor deposition (MOCVD) and atomic layer deposition (ALD) processes, TEMAZ[Zr(NMeEt)4: (tetrakis-ethylmethylamidozirconiums]can be exemplified (D. M. Hausmann et. al., Chem. Mater., 2002. 14, 4350).
TEMAZ is liquid at room temperature and has high vapor pressure, however it has low thermal stability and causes low step coverage and capacitor leakage. Accordingly, TEMAZ is to have the limits in adaptability either MOCVD process or ALD process for next generation semiconductor devices.
In ALD process, CpTDMAZ [cyclopentadienyltrisdimethylamidozirconium; CpZr(NMe2)3] is known as substitutive one of TEMAZ (Jaakko Niinisto et al. J. Mater. Chem. 2008, 18, 5243)
Paper describes that CpTDMAZ is liquid at room temperature and has high vapor pressure, and is more stable at high deposition temperature in comparison with TEMAZ. However, CpTDMAZ has demerits to produce undesirable by-products when it is applied in ALD process.
TDMAT [tetrakis-dimethylamidotitanium; Ti(NMe2)4] can be exemplified as a titanium compound which is most frequently applied in either MOCVD process or ALD process. And TEMAH [tetrakis-ethylmethylamidohafnium; Hf(NEtMe)4] can be exemplified as the hafnium compound. However, these compounds also cannot be used in next generation semiconductor devices due to same reasons with TEMAZ as described in above. Any substitute compound of TDMAT or TEMAH, which can be applied in ALD process, is not yet reported.
Atomic layer deposition (ALD) is a known thin film deposition method.
ALD comprises the steps of (1) vaporizing metalorganic compounds by heating a vessel containing them to around 100° C.˜110° C. for long hours and (2) transporting them to substrates as gaseous phase to deposit on substrate. However, during vaporizing and transporting steps, CpTDMAZ, TDMAT or TEMAH provides multi-component compounds via voluntarily intermolecular reactions. Accordingly when CpTDMAZ, TDMAT or TEMAH is applied, thickness control of thin film is difficult and good quality films cannot be obtained. As an alternative, liquid injection ALD is known, in which liquid compositions comprising metalorganic precursor compounds and their suitable stabilizing solvent such as hydrocarbons, ethers and amines are used as precursors.
Precursors forming 4B group metal oxides in CVD or ALD process are described below. But structures of these precursors are different those of novel 4B group metalorganic precursors of the present invention and their chemical properties are also different each other.    WO 2007/140813A1 (Dec. 13, 2007; Air LiquideSociete)    KR 2007/0121281A1 (Dec. 27, 2007; DNF)    KR 2010/0016477A1 (Feb. 12, 2010; Advanced Technology Materials)    D. M. Haussmann et. al., Chem. Mater., 2002, 14, 4350    Jaakko Niinisto et. al., J. Mater. Chem., 2008, 18, 5243